Inks and vehicles therefor



Patented Feb. 28, 1950 nvxs AND VEHICLES THEREFOR Harvey A. Sell,Rutherford, N. .L, and Herbert Cole, New York, N. Y.; said Sell assignorto said Cole No Drawing. Application July 30, 1946, Serial No. 687,234.In Canada January 2, 1942 7 Claims.

With so-called heat-set inks, useful for letterpress printing, agreat'excess of more or less toxic or noxious liquid solvent or diluentmust be driven off the printed sheet almost instantaneously.Complicated, costly and bulky heating, drying and ventilating equipmentare required for the purpose, to which but few presses are adapted and,moreover, the intense heatin required in such practice may adverselyaffect the folding, sealing, scoring and bending properties of thepaper. Though the solvent of heatset inks must be substantially blastedfrom the printed sheet, such ink nevertheless dries in air,necessitating frequent interruption of operations for washing hardenedink from the press.

So-called oxidizing inks having vehicles of drying or semi-drying oilsthat set by oxidation, require a day or more for the printed sheet todry sufiiciently for handling in subsequent operation such as printing afurther color, cutting, binding, or folding and, moreover the practiceof winding must be resorted to to prevent adhesion or sticking of thesheets due to the oxidation of the vehicle and to mitigate theobjectionable odor of the finished product. The addition of but a smallproportion of gums or resins has been feasible in an effort to improvefinish, adhesion and hard-- ness, and to shorten the drying time, forlarger proportions if soluble at all in such oils, result in a tacky andexcessively heavy body. The drying time of oxidizing inks with the useof such gum or resin ingredients has been shortened from twenty-fourhours or more down to in the neighborhood of an hour. But even were itpossible, with the addition of such gum or resin to accelerate thedrying time down to a period measured in seconds, rather than minutes,the evil of offsetting, smudging or sticking would still exist and slipsheeting, spraying or like expedients would still have to be resortedto, as would the practice of winding, and the operation would have to befrequently interrupted to permit the press to be cleaned and washed, dueto the drying of the ink thereon.

Among the objects of the present invention are to provide a printing inkwhich admits of multi or process color printing in a single pass throughalmost any multi-color press available at the present time and whichadmits of single color printing on any press, all without any danger ofsmudging, sticking or picking and which, following the application ofheat, as for instance, from one or more gas burners at the delivery endof the press, accomplishes delivery of the imprinted sheets in dry orset condition at all speeds of which the press is capable up to 5,000 ormore multi-color printed sheets per hour, with the abolition of all slipsheeting, spraying, racking, traying and also of the practice of windingthe sheets, and with the elimination of costly, bulky, elaborateequipment for heating or for ventilation, yet without hazard due tocombustible or toxic or noxious ingredients.

Another object is to provide a practically odorless printing ink, devoidof nitrocellulose or other highly inflammable ingredients, which may bestored for long periods without deterioration, which will not dry orcake on the press, and thus avoids the need for frequent washups andwhich develops no tackiness in drying.

Another object is to provide a vehicle for an ink of the above type,having the desired fluidity which may be stored for long periods andwithout deterioration due to skinning, hardening, livering or drying,despite the fact that the vehicle has a solvent content so small assubstantially to be completely absorbed by the paper as the imprint ishardened or set.

Another object is to provide a vehicle for an ink of the above typewhich admits of the use as the coloring medium not only of conventionalpigments but in lieu thereof of various dyes, by which economies andnovel efiects are attained as are other advantages including greaterexpedition in setting or drying and a homogeneous imprinted film orimpression with greater coverage. 1

This application is a continuation-in-part of our copending case, SerialNo. 369,122, filed December 17, 1940, now abandoned.

The invention involves the use of a new vehicle comprising essentially apartly polymerized alkyd resin, dissolved in a small proportion ofsolvent that is substantially non-volatile at room temperature, whichvehicle will carry dyes in solution therein in proportions fullyadequate-for any density of coloration, or alternatively will carry indispersion the pigments commonly used in printinginks, and which inkwill instantly set, harden, condense or polymerize when heated,

the small amount of solvent being substantially absorbed by the sheetbeing imprinted.

The vehicle in a desirable embodiment is a resin made from a mixture ofsaturated dibasic acid, polyhydric alcohol and higher fatty acid, themix being partially polymerized topredetermined degree, so that it issemi-plastic and not readily fiowable at room temperatures. Thesemiplastic prepared according to our teachings (that ai e more fullyset forth hereinafter), lends itself to thinning to the requiredfiowability for printing inks, by dissolving in ordinary inexpensivepetroleum hydrocarbon, preferably of the allphatic type that issubstantially non-volatile at room temperature.

The dibasic saturated acid may besuccinic, adipic or homologous acidstable under heat, but for general application phthalic anhydride ispreferred by reason of its low cost. An unstable acid such as malicwhich decomposes upon heating to the unsaturated maleic type is notwithin the scope of the designation dibasic saturated acid stable underhea The higher fatty acid ingredient may be any ordinary vegetable oilfatty acid which is commercially available. Such fatty acids arecommonly derived from soy beans, linseed, hempseed, castor, menhaden,tung or perilla oil and include largely oleic, linoleic and linolenicacid. The polyhydric alcohol may be a glycerol, a glycol, erythritol,pentaerythritol, mannitol or the like, but for general applicationglycerol has been found to be most economical at the present time.

We have found, after long experiment, that the vehicle base of desiredhigh solubility in aliphatic hydrocarbon solvent that is non-volatile atroom temperature, must be of substantially critical proportions,processed in a definitely controlled manner. Specifically we have foundthat the desired product results when substantially 3.5 moles oftrihydric polyhydric alcohol, 2.75 moles of phthalic anhydride and from1.0 to 1.5 moles of vegetable oil fatty acid are polymerized to thatpredetermined degree which is attained by slowly heating with agitation,taking approximately one hour to reach 230 degrees C. and thencontinuing to heat at approximately that temperature for three hours andfifteen minutes more with the introduction of inert gas. The activeradical of the polyhydricalcohol being the hydroxyls, the number ofhydroxyls in 3.5 moles is 10.5 from a molar standpoint. With polyhydricalcohols of lesser or greater hydroxyl .value, the molar equivalentswill be correspondingly greater or less to afford the same hydroxylvalue. .We are not familiar with any way of defining the degree ofpolymerization except by some .procedure such as that set forth forattaining it.

One particular formula -which in practice has been found especiallysuitable when processed as above set forth. is made up of the followingingredients in the following proportions by weight:

Parts Phthalic anhydride 81 Glycerine 64 Boy bean fatty acids 81vehicle, although it contains 65 per cent or more of solid matter andonly 35 per cent or less of solvent, nevertheless has the required lowviscosity for a printing ink vehicle. That a product including theseingredients involving the small fatty acid content prescribed, could besoluble to such extent in such aliphatic hydrocarbons was unexpectedboth by those skilled in the printing ink art and those skilled in theresin art. That property is an important factor in the utility of thevehicle as will appear more fully hereinafter.

Where a considerably larger proportion of fatty acid is used than abovespecified, while the solubility of the resultant vehicle base isenhanced, it dries slowly and therefore becomes unsuitable for purposesof the present invention. 0n the other hand, where a lesser amount offatty acid is used than herein specified, the resultant product becomespractically insoluble in aliphatic hydrocarbons and could be dissolvedonly in the more potent, more volatile and more costly solvent, with theobjections above pointed out.

If more heat is introduced into the mix than above specified, thepolymerization will be carried on to such degree that more solvent willbe required than can be absorbed by the paper in the absence of theevaporation equipment with which the present invention dispenses. 0n theother hand, if less heat be used, then the polymerization will becarried on only to such extent that even though less solvent be adequatefor solution of the product. the printed surface will remain tacky, andthe consequent higher acid number results in livering of color lakes.

The vehicle of the specifications set forth has one other surprisingproperty of high utility in printing inks and the like. It is anexcellent solvent for non-water soluble dyes that heretofore have beenfound to be soluble only in expensive, potent solvents such as glycolderivatives, esters or ethers, alone or in combination with benzenehydrocarbons such as benzene, toluene, xylene or the like. Though of theingredients as such of our vehicle, only the fatty acid is a solvent fordye bases, our vehicle composed of these ingredients, notwithstandingits extremely low acid number, readily dissolves, to the surprise ofthose skilledin the art, relatively large proportions of all color basedyes of the diaryl methane, the triaryl methane and the oil soluble azotypes.

,Among these are those of negrosine, rhodamine,

Victoria blue, malachite green and diazaphine yellow base. In fact suchdyes can be used in lieu of instead of merely as a supplement topigments. In general the amount of dye used is not less than one (1) andnot more than five. (5%) per cent of the weight of the vehicle to securethe maximum degree of coloration required, but con siderably largerproportions of most of said dyes are soluble in the vehicle withoutdanger of bein precipitated at low temperatures. Since the vehicle ofthe present invention is not acid in character, it admits of admixturealso with color lakes which would liver in an acid environment. The dyescould be dissolved in the vehicle after preparation of the latter, orafter preparation of the partially polymerized base and before addingthe solvent.

The dye has many advantages over the pigment coloring agent. Greatercoverage is obtained since the coloring pervades the film and lacks thediscrete particles of pigment inks. The imprinted film having no hard orgritty particles is homogeneous and will not scratch or rub.

By reason of the absence of vehicle absorbent pigment particles, moreexpeditious drying or setting of the dye colored ink results.Furthermore, the translucency of many dyes renders them more suitablefor certain process color printing effects. Finally, the absence ofsolid pigment particles obviates the filling of the screen in theprinting plate and the press requires less frequent washing and cleaningthan where pigment inks are used.

The vehicle set forth may be stored in containers indefinitely withoutchange in its physical or chemical characteristics and indeed can beexposed to the open air regardless of temperature without hardening,drying or other deterioration. It may be admixed by the manufacturer orby other processors with the necessary color and other ingredients toproduce the printing ink as required, with a solid content of preferablynot less than 65 per cent.

The formula above specified could be modifled, if desired, by reducingthe soy bean fatty acid ingredient from 81 parts to as little as 54parts. The ingredients of the modified formula are processed exactly asabove set forth to produce the partially polymerized resin. This,however, is not as readily soluble in petroleum hydrocarbon solvent asis the formula with the larger amount of fatty acids. The solution ofthe resin in the solvent is brought to pass by constant agitation of themix until slowly cooled to room temperature.

The ink of the present invention, whether in the pigment or the dyeembodiment may, depending upon the particular type of printing to bedone and the characteristics desired, be admixed with any or all ofvarious materials commonly used in the manufacture of printing inks suchas toners, extenders, fillers, wetting agents, waxes, compounds,thinners or reducers and driers, properly dispersed in the vehicle.

In use of the ink of the present invention, the thin film imprinted uponthe sheet in the ordinary manner dries or sets instantly as it passes aheater beyond the impression cylinder or platen of the press, the minoramount of solvent in the ink being in large part absorbed by the paper.Where a gas flame is used for the purpose, sumcient water vapor isevolved as a product of combustion to prevent dehydrating the papersheet or breaking down the fiber, so that it remains flexible and willnot crack in subsequent folding or bending. Such heater of sim ple,compact and inexpensive form is disclosed in the Cole Patent No.2,153,325 of April 4, 1939. The heat causes the partially polymerizedresin of the vehicle to "kick over that is materially to advance or tocomplete its polymerization, so that the imprint is substantiallycompletely dried or set by the time the sheet leaves the press. Anysmall excess of solvent beyond what the paper will absorb, will beincorporated in the polymerized resin or will evaporate. The imprintedpaper leaves the press in dry or set condition. The resin in setting ordrying under heat incorporates the pigment or dye with it, to produce awaterproof imprint, so intimately incorporated with the paper thatitdoes not rub off.

While the ink thus dries or hardens readily under the heat of the gasflame, it will not harden or dry at room temperature. This is due to thefact that the partially polymerized resin is of the type thepolymerization or condensation of which will not progress in the solventunder atmospheric conditions and also because the solvent issubstantially non-volatile at room temperature. Therefore, the ink mayreadily be'removed from the printing form and rollers of the press,without the difliculties incurred with so-called evaporating inks orwith oxidizing inks which progressively harden when exposed. For thisreason the ink can be stored indefinitely without deterioration and willnot harden or dry even though exposed to the air for some time.

By reason of its high solid content the ink can be laid down upon thepaper in multi or process color printing in one pass through anappropriate press, without the necessity for drying each colorapplication before applying the succeeding one. The gas heatingequipment at the delivery end of the press hardens, sets or polymerizesthe vehicle of the ink, whether applied in a single or in multipleimpressions. Sheets delivered from the press at the rate of even 5,000or more per hour may thus be directly stacked upon each other withoutdanger of offsetting, smudging, sticking or picking, with theelimination of slip sheeting, spraying, racking, traying or otherexpensive expedients intended to mitigate those evils. The ink beingsubstantially completely set as the sheet leaves the press, no materialfurther reaction occurs in the stack or roll of imprinted paper. Thedanger of sticking together that occurs with oxidizing inks isnon-existent and the practice of winding resorted to with oxidizing inksis not necessary, and the printed product has no objectionable odor.Thus, the excess space required in press rooms for work in process ofdrying or setting, and amounting in many cases to thirty per cent of thetotal floor space, may be dispensed with, without incurring thelimitations and hazards of costly and bulky installations necessarywith,

the so-called "heat-set or evaporating inks.

While the invention is especially advantageous for letterpress printingin single, multi or process color printing, it is not restricted to thisuse, but can be used on other types of presses with highly satisfactoryresults. In certain types of printing. especially upon soft or opensurface paper stock, the imprint will leave the press sufllciently hardand set, even though the heater be omitted.

advantageously in lieu of conventional linseed oil vehicle inkv and witheconomies and improved results. Where the heater is dispensed with andno means is provided for kicking over the partially polymerized resin, asuitable conventional tend to remain sticky on the sheet, so that intime the fllm would break or crack. Ester gum is prepared by theesterification with glycerin or other polyhydric alcohol of abieticacid, usually derived from colophony or rosin which is composed largelyof such acid and its anhydride. In some cases as much as three parts byweight of such ester gum may be used with one part of the partiallypolymerized vehicle base previously described and one part of thepetroleum hydrocarbon solvent. The viscosity of the resulting vehicle inthis case is considerably lower than that of a vehicle prepared eitherwith the alkyd resin The ink of the present invention may be used Alkydresin composed of Parts Phthalic anhydride 2'7 Glycerine 21 Boy beanfatty acid 27 The '75 parts of alkyd resin partially polymerized asabove set forth. are dissolved in some 3'! parts of aliphatichydrocarbon and Ester gum composed of Parts Abietic acid 135 Glycerine1'! The 150 parts of ester gum are dissolved in some 75 parts ofaliphatic hydrocarbon.

The mixture of alkyd resin and ester gum solutions is found to have aviscosity lower than either of the component solutions. The same is trueif the ratio of ester gum to alkyd resin is changed from that of theabove illustrative example to as much as 3 to 1.

The term polymerization as used in the broader claims is not confined toany closely limited technical meaning, but defines the molecularaggregation or conglomeration that occurs in the formation of plastic orsemi-plastics from raw materials, regardless whether this be due topolymerization in the narrow sense of the term or to other chemical orphysical action, such as condensation or combination of various actions.

While the invention has been described in its application as a printingink for which purpose it has outstanding utility, it will be understoodthat it is useful in other branches of the graphic arts, for imprintingnot only paper but other materials including textiles, wood, metal, etc.

As many changes could be made in the above vehicle, ink and process andmany apparently widely difierent embodiments of this invention could bemade without departing from the scope of the claims, it is intended thatall matter contained in the above description, shall be interpreted asillustrative and not in a limiting sense.

Having thus described our invention what we claim as new and desire tosecure by Letters Patent of the United States is:

l. A vehicle for a printing ink, consisting of substantially two partsby weight of partially polymerized resin dissolved in about one part byweight of aliphatic hydrocarbon solvent that is substantiallynon-volatile at room temperature. said partially polymerized resin beingmade by reacting a mixture consisting of 2.75 moles of phthalic acidanhydride, 1 to 1.5 moles of vegetable oil fatty acid, and polyhydricalcohol of hydroxyl value substantially equal to that of 3.5 moles ofglycerol, and in which the alcoholic hydroxy groups are the solereactive groups, said resin being partially polymerized by slow heatingof the said ingredients with agitation, taking approximately one hour toreach 230 C. and then continuing to heat the same approximately at thattemperature for three hours and fifteen minutes more.

2. The vehicle recited in claim 1 which includes not more than threeparts by weight of ester gum to one partof the resin, said ester gumbeing also dissolved in aliphatic hydrocarbon solvent.

3. The combination recited in claim 1 in which 8 the aliphatichydrocarbon solvent has a boiling range between 500 degrees and 600degrees I".

4. A vehicle for a printing ink consisting of not more than three partsby weight of ester gum to one part of alkyd resin, said ester gum andresin being dissolved in aliphatic hydrocarbon substantiallynon-volatile at room temperature, said solution being substantially ofthe resin and gum to substantially 35% of the solvent, said allwd-resinbeing made by reacting a mixture consisting by weight of substantially21 parts of glycerin, 27 parts of phthalic acid anhydride. and 27 partsoi vegetable oil fatty acid, said resin being partially p lymerized byslow heating of the said ingredients with agitation taking approximatelyone hour to reach 230 C. and then continuing to heat the sameapproximately at that temperature for three hours and fifteen minutesmore.

5. A printing ink consisting of substantially two parts by weight ofresin dissolved in one part by weight of aliphatic hydrocarbon solventthat is substantially nonvolatile at room temperature, said solutionconstituting a vehicle having dissolved therein coloring matterconsisting of basic dyes selected from the group consisting of diarylmethane, triaryl methane, and the oil soluble azo dyes, said resin beingmade by reacting a mixture consisting of 1 to 1.5 moles of vegetable oilfatty acid. p lyhydric alcohol with hydroxyl value substantially equalto that of 3.5 moles of glycerol and in which the alcoholic hydroxygroups are the sole reactive groups, and 2.75 moles of acid compoundselected from the group consisting of phthalic acid anhydride and stablesaturated carboxylic dibasic acid, in which the carboxyl groups are thesole reactive groups, said resin being partially polymerized by slowheating of the ingredients with agitation taking approximately one hourto reach 230 C. and then continuing to heat the same approximately atthat temperature for three hours and fifteen minutes more.

6. A printing ink consisting of substantially two parts by weight ofresin dissolved in one part by weight of aliphatic hydrocarbon solventthat is substantially non-volatile at room temperature, said solutionconstituting a vehicle having dissolved therein coloring matter of fromone to five per cent of the weight of the ink, and consisting of basicdye bases selected from the group consisting of diaryl methane, triarylmethane, and the oil soluble azo dyes, said resin being made by reactinga mixture consisting of 2.75 moles of phthalic acid anhydride, 1 to 1.5moles of vegetable oil fatty acid, and polyhydric alcohol of hydroxylvalue substantially equal to that of 3.5 moles of glycerol, and in whichthe alcoholic hydroxy groups are the sole reactive groups, said resinbeing partially polymerized by slow heating of said ingredients withagitation taking approximately one hour to reach 230 C. and thencontinuing to heat the same .approximately at that temperature for threehours and fifteen minutes more.

7. A printing ink consisting of a vehicle base comprising one part ofresin to not more than three parts by weight of ester gum, said printingink having a vehicle comprising substantially 65% of said vehicle basedissolved in substantially 35% of aliphatic hydrocarbon substantiallynon-volatile at room temperature, said vehicle having in solutiontherein coloring matter of from one to five per cent of the weight ofthe ink, and consisting of basic dye bases selected 9 10 from the groupconsisting of the diaryl methane, REFERENCES CITED triaryl methane, andthe oil soluble azo dyes, said resin being made by reacting a mixtureconsist- $2 g i fj are of record m the ing by Weight of substantially 21parts of glycerin, 27 parts of phthalic acid anhydride and 27 parts 5UNI ED STATES PATENTS of vegetable oil fatty acid, said resin being par-Number Name Date tially polymerized by slow heating of said ingredi- 2070 278 Kelly Feb 9 1937 ents with agitation taking approximately one2074814 Smith M 1937 hour to reach 230 C. and then continuing to heat2153511 g i Er 1939 the same approximately at that temperature for 102:285:430 Gessler et a1 1942 three hours and fifteen minutes more.

FOREIGN PATENTS HARVEY A- SEIL- Number Country Date HERBERT COLE-337,199 Great Britain Oct. 30, 1930

1. A VEHICLE FOR A PRINTING INK, CONSISTING OF SUBSTANTIALLY TWO PARTSBY WEIGHT OF PARTIALLY POLYMERIZED RESIN DISSOLVED IN ABOUT ONE PART BYWEIGHT OF ALIPHATIC HYDROCARBON SOLVENT THAT IS SUBSTANTIALLYNON-VOLATILE AT ROOM TEMPERATURE, SAID PARTIALLY POLYMERIZED RESIN BEINGMADE BY REACTING A MIXTURE CONSISTING OF 2.75 MOLES OF PHTHALIC ACIDANHYDRIDE, 1 TO 1.5 MOLES OF VEGETABLE OIL FATTY ACID, AND POLYHYDRICALCOHOL OF HYDROXYL VALUE SUBSTANTIALLY EQUAL TO THAT OF 3.5 MOLES OFGLYCEROL, AND IN WHICH THE ALCOHOLIC HYDROXY GROUPS ARE THE SOLEREACTIVE GROUPS, SAID RESIN BEING PARTIALLY POLYMERIZED BY SLOW HEATINGOF THE SAID INGREDIENTS WITH AGITATION, TAKING APPROXIMATELY ONE HOUR TOREACH 230*C. AND THEN CONTINUING TO HEAT THE SAME APPROXIMATELY AT THATTEMPERATURE FOR THREE HOURS AND FIFTEEN MINUTES MORE.